Gelatin has a wide range of commercial utility. For example, gelatin is used in wet processed photographic emulsions, pharmaceutical dosage forms, cosmetics (binder), and a wide range of food products. Gelatin has many useful physical and chemical properties that support this broad range of utility.
Gelatin is manufactured by the hydrolysis of animal by-products that contain collagen. This is usually found in animal bones, skins, and connective tissue. The collagen containing material is heated in water and the liquor produced is concentrated and dried, leaving behind the colorless or pale yellow protein that constitutes the hydrophilic colloid material known as gelatin.
The primary sources of gelatin are from bovine and swine animals. Additionally, fish and poultry are alternative small volume sources of gelatin. The source of gelatin can be a problem for potential areas of use or for particular consumers. Large groups around the world choose not to ingest any products of pigs (e.g., vegetarians, Hebrews, and Muslims) or the products of beef (e.g., vegetarians and Hindus). As medication and/or diet supplements are provided in gelatin capsules without any indication of the source of the gelatin, the use of capsules is restricted in areas where religious beliefs question the source of the gelatin. Additionally, due to reported possibilities of cross-contamination of diseases among species, for example bovine spongiform encephalopathy (“BSE” or “Mad Cow Disease”), the use of uncontrolled by-products from animals has lost some level of commercial acceptance. In short, there is a need for replacement compositions for gelatin that are not derived from animal sources.
Gelatin is a protein hydrocolloid. Hydrocolloids are hydrophilic colloidal materials that readily absorb water. Types of non-gelatin hydrocolloids include plant exudates, seaweed extracts, plant seed gums or mucilages, cereal gums, fermentation gums, modified cellulose, and modified starches. Non-gelatin hydrocolloids suitable for inclusion in a film-forming composition according to the invention include, but are not limited to, carrageenan, alginates, agar, guar, pectin, locust bean gum, xanthan gum, unmodified starch, modified pregelatinized starch, and gellan gum. Carrageenan is particularly useful in producing a non-gelatin film according to the invention.
Carrageenan is a natural polysaccharide hydrocolloid derived from red seaweed of the species Rhodophycea. Carrageenan is a carbohydrate polymer of repeating galactose and 3,6-anhydrogalactose (sugar) units that is linear and without significant numbers of branches or substitutions. Most, if not all, of the galactose units on a carrageenan molecule possess a sulfated ester group. The exact position of the sulfate groups, the cations on the sulfate groups, and the possible presence of an anhydrous bridge on the molecule differentiate the various types of carrageenan.
There are five distinct types of carrageenan, each of which behaves differently and has distinct properties. The types of carrageenan are iota, kappa, lambda, mu and nu carrageenan. These types of carrageenan can significantly vary in properties. For example, lambda carrageenan in solution is unable to associate into a structure, and therefore is unable to form a gel, but nonetheless acts as a thickener. Both kappa and iota carrageenan, the predominant carrageenan types, are capable of forming gels. Kappa carrageenan is known to form strong gels in the presence of potassium cations. However, kappa carrageenan gels tend to be brittle and exhibit syneresis (exudation of the liquid portion of the gel). Iota carrageenan tends to react strongly to calcium cations and forms a weaker and more flexible gel than kappa carrageenan. Iota carrageenan is not as susceptible to syneresis as kappa carrageenan. Mu and nu carrageenan are thought to be precursors of kappa carrageenan and iota carrageenan, respectively, and may be present only in very small quantities as impurities in pure kappa and iota carrageenan. Mu and nu carrageenan are not of commercial importance.
The type of carrageenan used affects the physical properties of the final gel or film. WO 99/07347 and WO 01/03677 describe gel forming compositions that have iota carrageenan as the sole gelling agent. Despite the fact that kappa carrageenan is also able to gel, these publications teach that kappa carrageenan is detrimental when the end product desired is a film for capsule manufacture, The phenomenon of syneresis and the fact that kappa carrageenan forms brittle gels are cited as reasons for avoiding the use of kappa carrageenan in such films.
When forming a film for subsequent use in medicinal, cosmetic, or nutritional capsule manufacture, the resultant physical properties of sealability, extensibility, and tensile strength are important. Thus, a gelling composition comprising carrageenan or other non-gelatin hydrocolloids must provide adequate physical properties useful in manufacturing. Kappa carrageenan is a less expensive starting material as compared to iota carrageenan. Thus, it would be beneficial to develop a gel- or film-forming composition comprising kappa carrageenan and iota carrageenan, wherein the resultant film provides the requisite physical properties for capsule manufacture.
Processes to manufacture capsules from carrageenan and starch-based shell materials have been very limited. By nature, commercial powder forms of carrageenans and other hydrocolloids require a large percentage of water to fully hydrate. Unfortunately, the strength of a film made from these materials at a water content necessary to fully hydrate the hydrocolloids is not as strong as desired for use in established enrobement and encapsulation processes. To facilitate production of edible films in a production environment, it is sometimes beneficial to add additional amounts of water to a film-forming formula than is strictly required to hydrate the hyrdrocolloids. This additional water reduces the viscosity of the mixture, thereby permitting the mixture to flow under gravity for subsequent processing. Unfortunately, this high water content substantially reduces the strength of films produced from such the mixture.
One method of producing non-gelatin films includes casting these materials at high water content into a film, then drying the film prior to use for encapsulation. Unfortunately, such processes are less than optimal due to the long time that is required to dry the films to a usable level for encapsulation. For this reason, production quantities of capsules have not been made using such a process. Other methods for producing non-gelatin films do not include a drying step prior to encapsulation. Instead, high volumes of carrageenan (approximately 10%) are used to achieve the strength required for capsule manufacture. Such high quantities of carrageenan are undesirable, however, due to the high cost of the material. Such a process also limits the variations in film formula that are available to produce capsules with specific properties such as hardness. Such a process also include a melt on demand system that utilizes a pressurized system to help move the film material to a transfer pump to be processed. This pressurized system is necessary because the high quantity of carrageenan used in the film formula gives the mass a very high viscosity. The pressurized process is also necessary because the gel temperature of the film-forming material at high concentrations of carrageenan necessarily is very high. Unfortunately, holding the mass at this high temperature for an extended period of time as is typically required for production encapsulation causes an undesirable breakdown of the hydrocolloids in the film-forming mixture.
Accordingly, there is a need for a process that permits the use of a variety of types and concentrations of hydrocolloids and permits the viscosity of a film-forming composition to be sufficiently low such that the composition can flow under gravity. It is also desirable to have a process for producing films comprising many types of hydrocolloids that permits a film-forming composition comprising such hydrocolloids to be processed at temperatures that do not cause substantial degradation of the film-forming materials.